The interaction of the sulfide mineral flotation collector, O-isopropyl-N-ethylthionocarbamate (IPETC), with copper surfaces has been investigated by surface enhanced Raman scattering (SERS) spectroscopy. Adsorption of IPETC has been shown to involve a charge transfer process in which the sulfur atom in the organic species becomes bonded to a copper atom in the metal surface and the hydrogen is displaced from the nitrogen atom to form a hydrogen ion in solution. IPETC and copper IPETC compounds were characterised by 13C NMR and Raman spectroscopy to provide a basis for identifying surface species. The formal potential for the Cu ∣ IPETC system in acid and neutral solutions was found to be 0.131 V and the dependence of the reversible potential on IPETC concentration and on pH to be in agreement with the proposed mechanism. The SERS investigations showed that adsorption of IPETC commenced at a potential more than 0.31 V below the reversible value for the formation of the bulk copper compound; this behaviour is analogous to that previously found for the adsorption of other thiol collectors on metal and sulfide mineral surfaces. An estimate is made of the potential dependence of the interaction of IPETC with chalcocite.